After the Browns hired Ray Horton as their defensive coordinator Jan. 18, the first phone call he received was from linebacker D’Qwell Jackson.

Horton immediately knew Jackson, an eight-year NFL veteran and the longest-tenured member of the Browns, meant business. He also realized that Jackson would become an invaluable asset in helping the team convert from the 4-3 scheme employed by former defensive coordinator Dick Jauron to his 3-4, multifront system.

“He just said, ‘Coach, you tell us what to do, and we’ll do it. We’re tired of losing,’ ” Horton said, reflecting on his conversation with Jackson. “So it gives you that clay to mold because they weren’t set in their ways, they weren’t wretched, they weren’t going to fight, meaning fight what we do. He is unquestionably the leader of this team, and what he says goes here.”

Through their first five games this season, the Browns have transitioned to Horton’s defense with far greater success than most outsiders thought they would because there is usually an adjustment period of a season or two before a team adopts a new scheme and begins to flourish in it. No matter who has played quarterback and regardless of whether the special-teams units have delivered game-changing plays, the defense has been the most consistent and most reliable part of the Browns, who improved to 3-2 by defeating the Buffalo Bills 37-24 Thursday night at FirstEnergy Stadium.

Heading into Sunday, the Browns had the NFL’s fifth-ranked defense (301.8 yards allowed per game). It ranked eighth against the run (94.2 rushing yards allowed per game), ninth against the pass (207.6 passing yards allowed per game) and ninth in points allowed (18.8 per game).

“I think they’re taking a sense of ownership and a sense of pride, and it’s something that they want to show statistically that they are doing better,” Horton said. “I think they want to show it’s not just a fluke. It’s that we’re working hard to get better.”

Aside from Horton, Jackson might be most responsible for the success.

“I understand we have a younger team,” Jackson said. “What I try to do is learn the system better than anyone. I have to know what we’re doing on the defensive side of the ball better than anyone. Whatever knowledge I can teach a young guy, whatever info I can give a guy throughout the course of the game, that’s most important because throughout the week, everyone studies certain tendencies, but we all know when the game starts, they have a plan for you as well.

“So when you grow in this league, you’re able to figure out how the offense is attacking you that day. That’s what I try to do for the young guys. That’s the experience that I can give to them. I don’t feel like I have to do more with a new [coaching] staff because we have great leaders in the right positions.”

Jackson, the defense’s captain, certainly takes pride in being one of those great leaders. Every Friday after practice, he leads a players-only defensive meeting at the team’s headquarters.

“You hear your coaches every week,” Jackson said. “When you have players running the meeting, and everyone is involved, it builds that accountability and it builds that trust with one another. If we see something and we have a question about anything, we’ll go to coach with it, and that’s what the gist of that meeting is all about.”

Horton not only encourages his players to submit questions to the coaching staff but also plays they have designed. Horton called a play created by nose tackle Phil Taylor during a preseason game Aug. 15 against the Detroit Lions, the Browns’ next opponent who’ll visit FirstEnergy Stadium Oct. 13.

“It’s one of those ownership things where they feel empowered that they can have their own meetings and run things and suggest things and draw up plays,” said Horton, a former defensive back who played for the Cincinnati Bengals and Dallas Cowboys. “They’ve really bought into our system, and obviously we’re having success, so I think they see that the system works. And when they get to have input into plays, not only what we call, but them designing plays for us, it feels like it’s their team.”

Jackson, 30, has clicked with Horton from the start, and their chemistry has been a catalyst for the defense’s improvement. Last season, the defense ranked 23rd overall (363.8 yards allowed per game), tied for 18th against the run (118.6 rushing yards allowed per game), ranked 25th against the pass (245.2 passing yards allowed) and finished 19th in points allowed (23.0).

“I’m trying to learn as much as I can from [Horton],” said Jackson, who bounced back from two torn pectoral muscles he suffered in 2009-10 and has started every game since the 2011 season began. “He’s one of the smartest if the not the smartest coach I’ve played for in terms of scheme, in terms of putting guys in the right position, in terms of getting everything out of us when you turn the tape on and watch what our game was all about. He’s not a complicated guy. He doesn’t run a complicated scheme. Whatever we’re good at, we’re going to run it. He’s going to tell you how we’re going to attack teams, and that’s what we’re going to do.”

Many believed the 6-foot, 240-pound Jackson would not be as effective as an inside linebacker in Horton’s scheme as he was the past two seasons as a middle linebacker in Jauron’s 4-3 system. But Jackson has 49 tackles, 21 more than any other Browns player and the most in the NFL entering Sunday, two passes defensed and a forced fumble.

“D’Qwell studies day in and day out, and he’s a perfectionist,” Horton said. “For us, we just knew that he could play football, and it doesn’t really matter what scheme you play. You make a call and let your players do it. If anybody ever says, ‘He’s not this type of player,’ I’m like, ‘Is he a football player? Let’s just go play football.’ Now obviously you’ve got to call different things and then suit what they do best, but it’s still football. It’s still tackling when it comes down to it, and he is a gifted athlete.”

“DQ is a great leader,” strong safety T.J. Ward said. “He makes the defense move. He is the heart and soul of our defense, and what he says goes. If you follow him, you are following someone who’s doing everything right. He is going to leave his heart and soul on the field. That’s what you want from a leader. I think that his mentality is shaping and forming the rest of the defense.”

He embodies everything Horton wants from the defense.

“He’s really instrumental in changing the culture with us,” Horton said. “This is what it takes to be a championship-caliber type defense, and he’s been really an extra coach on the field for me.”

Perhaps Jackson will follow Horton’s footsteps and become a coach after his playing days.

“What I’m going to say to that is I have too much ball to play right now,” Jackson said with a smile. “I’ll think about that when that time comes.”